Modern motor vehicles are equipped with numerous vehicle subsystems that are designed to increase the comfort and safety of drivers and passengers. For example, a vehicle can include an anti-lock braking system, a traction control system, a speed control system, and/or a vehicle stability enhancement control system. In turn, each subsystem can include numerous electrically-operated hydraulic actuators that use electric coils to move plungers and thereby direct hydraulic fluid to and from vehicle components such as a brake.
As recognized herein, the movement of a plunger in a hydraulic electro-mechanical valve can be retarded by the presence of hydraulic fluid in and around the plunger's passage, which represents a damping effect on plunger movement. This problem is of particular concern in systems that require very quick plunger movement. To address the problem, the plunger can be shaped to promote the relative motion of the fluid past the plunger.
As recognized herein, however, this approach not only can lead to performance degradation, but can require relatively costly manufacturing techniques. For instance, shaping the plunger typically requires removing plunger material, entailing costly machining, and the removal of plunger material undesirably reduces the electromagnetic coupling between the plunger and the activating electrical coil. The present invention has recognized these drawbacks, and has provided the below-disclosed solutions to one or more of them.